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Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature

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Chinese Physics B 2014年第4期23卷 545-550页

作者： Ibrahim Ycedag Ahmet Kaya Semsettin Altindal Ibrahim Uslu department of Computer Engineering Technology Faculty Duzce University department of Opticianry Vocationel School of Medical Sciences Turgut Ozal University department of Physics Faculty of Science and Arts Gazi University department of Chemistry Faculty of Science and Arts Gazi University

In order to investigate of cobalt-doped interracial polyvinyl alcohol （PVA） layer and interface trap （Dit） effects, A1/p- Si Schottky barrier diodes （SBDs） are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance （Rs）, and interfacial layer. Both the real and imaginary parts of dielectric constant （er and err） and electric modulus （Mr and Mrr）, loss tangent （tan~）, and AC electrical conductivity （aac） are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance （C） and conductance （G/w） values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si （MPS） type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance （CLF-CHF） method.

关键词： Al/Co-PVA/p-Si (MPS) electrical and dielectric properties AC electrical conductivity frequencyand voltage dependence

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Jet energy loss and bulk parton collectivity in nucleus-nucleus collisions at RHIC

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Chinese Physics C 2009年第6期33卷 456-462页

作者：黄焕中 department of Physics and Astronomy University of California department of Engineering Physics Tsinghua University

Nucleus-nucleus collisions at RHIC produce high temperature and high energy density matter which exhibits partonic degrees of freedom. We will discuss measurements of nuclear modification factors for light hadrons and non-photonic electrons from heavy quark decays, which reflect the flavor dependence of energy loss of high momentum partons traversing the dense QCD medium. The dense QCD medium responds to energy loss of high momentum partons in a pattern consistent with that expected from a hydrodynamic fluid. The hadronization of bulk partonic matter exhibits collectivity with effective partonic degrees of freedom. Nuclear collisions at RHIC provide an intriguing environment, where many constituent quark ingredients are readily available for possible formation of exotic particles through quark coalescence or recombinations.

关键词： relativistic heavy ion collision

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Kinetics of aggregation growth with competition between catalyzed birth and catalyzed death

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Chinese Physics B 2008年第4期17卷 1490-1500页

作者：王海锋林振权高艳 Key Laboratory Ecophysics and department of Physics Teachers CollegeShihezi University department of Physics Wenzhou University

An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with theconstant rate kernels In（n = 1,2, 3）. Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K（k, j） = Kkj^v, and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L（k, j） = Lkj^v, whcre v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species ak （t） is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species：（i） In the v 〈 0 case, the irreversible aggregation dominates the process, and ak（t） satisfies the conventional scaling form; （2） In the v ≥ 0 casc, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, ak（t） takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely.

关键词： kinetic scaling behaviour aggregation growth catalyzed birth and death rate equation

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High permittivity and low dielectric loss analysis of lead free Sr_(1-x)La_x(Ti_(0.5) Fe_(0.5))O_3

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Journal of Central South University 2013年第12期20卷 3363-3371页

作者： M.R.Shah A.K.M.Akther Hossain department of Physics Primeasia University department of Physics Bangladesh University of Engineering and Technology

The structural and electrical properties of lead free Srx-xLax（***.5）O3 （SLTFO） prepared by standard solid state reaction technique were studied. The X-ray diffraction analysis confirmed the formation of a single-phase cubic perovskite structure. The compositional dependence of lattice constant, density and microstructural studies show that they vary significantly with La3＋ content. When measured at 10 kHz, all the compositions of SLTFO at room temperature exhibit a high permittivity （about 104） and low dielectric loss （about 10-3）. SLTFO also display minimum dielectric loss within the lower and higher limits of frequency, indicating that the samples are of good quality. It is concluded from the calculated ac conductivity that the conduction is due to mixed polarons hopping. The complex impedance plot exhibits a tendency of forming a single semicircular arc for all compositions, which implies a dominance of grain boundary resistance on the impedance. Impedance parameters were determined by fitting the experimental data with Cole-Cole empirical formula. The results of the present experiment indicate that the lead free SLTFO materials with higher permittivity and lower dielectric loss have possible practical applications.

关键词： dielectric properties solid state reaction Sr titanate X-ray diffraction

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Analysis of the wave properties of a new two-lane continuum model with the coupling effect

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Chinese Physics B 2012年第1期21卷 295-309页

作者： Arvind Kumar Gupta Sapna Sharma department of Mathematics Indian Institute of Technology Ropar department of Mathematics Birla Institute of Technology & Science Pilani

A multilane extension of the single-lane anisotropic continuum model （GK model） developed by Gupta and Katiyar for traffic flow is discussed with the consideration of the coupling effect between the vehicles of different lanes in the instantaneous traffic situation and the lane-changing effect. The conditions for securing the linear stability of the new model are presented. The shock and the rarefaction waves, the local cluster effect and the phase transition are investigated through simulation experiments with the new model and are found to be consistent with the diverse nonlinear dynamical phenomena observed in a real traffic flow. The analysis also focuses on empirically observed two- lane phenomena, such as lane usage inversion and the density dependence of the number of lane changes. It is shown that single-lane dynamics can be extended to multilane cases without changing the basic properties of the single-lane model. The results show that the new multilane model is capable of explaining some particular traffic phenomena and is in accordance with real traffic flow.

关键词： two-lane traffic numerical simulation lane usage inversion

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A structural relationship between place attachment and intention to conserve landscapes–a case study of Harz National Park in Germany

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Journal of Mountain Science 2017年第5期14卷 998-1007页

作者： Dukjae LEE Ju-Hyoung LEE department of Forest Resources University of Daegu department of Forest Resources Yeungnam University

Place attachment is an important motivation for people to spend more time outdoors and to protect *** study explores visitors' intention to conserve natural landscapes based on the relationship with their place attachment to National Park landscape. Structural equation modelling(SEM) was used to determine the relationship between landscape conservation and place attachment. A survey with a structured questionnaire was administered to visitors to the seven designated hiking courses of Harz National Park in Germany. The path coefficient of 0.77 revealed that place dependence positively and significantly affected place attachment, whereas place identity did not. Place attachment had a significant effect on both affective appraisals and visiting satisfaction. Higher place attachment led to higher emotional reaction to landscapes on site and higher satisfaction of visiting the park. Among the variables, visiting satisfaction, but not affective appraisals, played a statistically significant mediating role between place attachment and conservation intention. With a path coefficient of 0.86, conservation intention was highly affected by visiting satisfaction. These results suggest that the managers of National Parks should focus on increasing visiting satisfaction based on how visitors are emotionally bonded with their visiting places, in order to enhance the intentions to conserve the landscape of the visitors to National Parks.

关键词： Place attachment Sense of place Mountain forests Structural Equation Model Landscape preference

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Effect of Co doping on structural, optical, electrical and thermal properties of nanostructured ZnO thin films

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Journal of Semiconductors 2015年第3期36卷 35-40页

作者： Sonet Kumar Saha M.Azizar Rahman M.R.H.Sarkar M.Shahjahan M.K.R.Khan department of Physics Bangladesh University of Engineering and Technology department of Physics University of Rajshahi

Nanocrystalline Zn1-x CoxO（where x varies from 0 to 0.04 in steps of 0.01） thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction patterns confirm the formation of hexagonal wurtzite structure. The crystal grain size of these films was found to be in the range of 11–36 nm. The scanning electron micrographs show a highly crystalline nanostructure with different morphologies including rope-like morphology for undoped ZnO and nanowalls and semispherical morphology for Co-doped Zn O. The transmittance increases with increasing Co^2＋ doping. The optical absorption edge is observed in the transmittance spectra from 530 to 692 nm, which is due to the Co2C absorption bands corresponding to intraionic d–d^＊ shifts. The direct and indirect optical band gap energies decrease from 3.05 to 2.75 eV and 3.18 to 3.00 eV, respectively for 4 mol% Co doping. The electrical conductivity increases with increasing both the Co doping and temperature, indicating the semiconducting nature of these films. The temperature dependence thermal electromotive force measurement indicates that both undoped and Co-doped ZnO thin films show p-type semiconducting behavior near room temperature. This behavior dies out beyond 313 K and they become n-type semiconductors.

关键词： ZnO:Co thin films structural properties optical properties electrical properties thermal properties

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Self-normalization:Taming a wild population in a heavy-tailed world

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Applied Mathematics(A Journal of Chinese Universities) 2017年第3期32卷 253-269页

作者： SHAO Qi-man ZHOU Wen-xin department of Statistics The Chinese University of Hong Kong department of Mathematics University of California

The past two decades have witnessed the active development of a rich probability theory of Studentized statistics or self-normalized processes, typified by Student’s t-statistic as introduced by W. S. Gosset more than a century ago, and their applications to statistical problems in high dimensions, including feature selection and ranking, large-scale multiple testing and sparse, high dimensional signal detection. Many of these applications rely on the robustness property of Studentization/self-normalization against heavy-tailed sampling distributions. This paper gives an overview of the salient progress of self-normalized limit theory, from Student’s t-statistic to more general Studentized nonlinear statistics. Prototypical examples include Studentized one- and two-sample U-statistics. Furthermore, we go beyond independence and glimpse some very recent advances in self-normalized moderate deviations under dependence.

关键词： Berry-Esseen inequality Hotelling’s T 2-statistic large deviation moderate deviation self-normalization Student’s t-statistic U-statistic

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Studying thin film damping in a micro-beam resonator based on non-classical theories

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Acta Mechanica Sinica 2016年第3期32卷 369-379页

作者： Mina Ghanbari Siamak Hossainpour Ghader Rezazadeh Mechanical Engineering department Sahand University of Technology Mechanical Engineering department Faculty of Engineering Urmia University

In this paper, a mathematical model is presented for studying thin film damping of the surrounding fluid in an in-plane oscillating micro-beam resonator. The proposed model for this study is made up of a clamped-clamped micro-beam bound between two fixed layers. The microgap between the micro-beam and fixed layers is filled with air. As classical theories are not properly capable of predicting the size dependence behaviors of the micro-beam,and also behavior of micro-scale fluid media, hence in the presented model, equation of motion governing longitudinal displacement of the micro-beam has been extracted based on non-local elasticity theory. Furthermore, the fluid field has been modeled based on micro-polar theory. These coupled equations have been simplified using Newton-Laplace and continuity equations. After transforming to non-dimensional form and linearizing, the equations have been discretized and solved simultaneously using a Galerkin-based reduced order model. Considering slip boundary conditions and applying a complex frequency approach, the equivalent damping ratio and quality factor of the micro-beam resonator have been obtained. The obtained values for the quality factor have been compared to those based on classical theories. We have shown that applying non-classical theories underestimate the values of the quality factor obtained based on classical theo-ries. The effects of geometrical parameters of the micro-beam and micro-scale fluid field on the quality factor of the resonator have also been investigated.

关键词： Thin film damping micro-electromechanical systems(MEMS) Micro-polar theory

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Vibrations of FGM thin cylindrical shells with exponential volume fraction law

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Applied Mathematics and Mechanics(English Edition) 2009年第5期30卷 607-615页

作者： Abdul Ghafar Shah Tahir Mahmood Muhammad Nawaz Naeem department of Mathematics The Islamia University of Bahawalpur department of Mathematics Government College University

In this paper, the influence of an exponential volume fraction law on the vibration frequencies of thin functionally graded cylindrical shells is studied. Material properties in the shell thickness direction are graded in accordance with the exponential law. Expressions for the strain-displacement and curvature-displacement relationships are taken from Love＇s thin shell theory. The Rayleigh-Ritz approach is used to derive the shell eigenfrequency equation. Axial modal dependence is assumed in the characteristic beam functions. Natural frequencies of the shells are observed to be dependent on the constituent volume fractions. The results are compared with those available in the literature for the validity of the present methodology.

关键词： functionally graded material (FGM) vibration cylindrical shell Rayleigh- Ritz method exponential volume fraction law

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